1. Field of the Invention
The present invention relates to a pre-plasticizing type injection molding machine which includes a plasticizing device separately from an injection device, and control method therefor.
2. Description of the Related Art
Conventionally, as an injection molding machine for molding a composite resin, in which an additive material, such as magnetic metal pieces, glass fiber, pigment and so forth, is admixed with a synthetic resin, a mixing injection molding apparatus has been disclosed in Japanese Examined Patent Publication No. Heisei 7(1995)-106586.
The mixing injection molding apparatus disclosed in the above-identified publication is called as a screw and screw type pre-plasticizing injection molding machine. Such injection molding apparatus has a separate plasticizing device (kneading machine) in addition to a general in-line screw-type injection molding machine (injection machine). A molding material supplied from a hopper is sufficiently plasticized and mixed by a screw rotating in a barrel. Furthermore, the material is mash-sheared by a stationary disc and a rotary disc by a dividing-and-distributing action. In the injection molding machine, a molten resin (composite resin) supplied from the plasticizing device is measured and injected.
However, in the above-mentioned conventional mixing injection molding apparatus, in order to operate the plasticizing device in synchronism with the molding operation cycle of the injection apparatus, the operation of the plasticizing device cannot be continuous and inherently becomes intermittent. Therefore, the performance of the plasticizing device cannot be maximized. Therefore, there is a limitation in enhancing the degree of mixing and uniformity of the composite resin to make it impossible to obtain a high and uniform quality molded product.